Gaseous discharge device



Au 28-, 1934. c G FOUN 1,971,907

GASEOUS D ISCH ARGE DEVI CE Original Filed July 2, 1928 Inventor-zClifton G.F'o u rid.

I ZZA/ HisAttorneg.

Patented Aug. 28, 1934 T OFFICE GASEOUS DISCHARGE DEVICE Clifton G.

New York Found, Schenectady, to General Electric Company,

N. Y., asslgnor a corporation of Application July 2, 1928, Serial No.289,696

.. Renewed. October 26, 1933 5 Claims. (01. 176-122) The presentinvention relates to electrical discharges in gases, and in particularcomprises new gaseous glow devices adapted for operation withalternating current.

It is the object of my invention to provide a convenient form ofthermionic arc device for illumination or other purpose, which will beoperable with alternating current at ordinary distribution potentials.

Prior to my invention electric discharge devices having a positivecolumn of high luminosity have been constructed for operation withalternating current by providing two anodes together with a singlecooperating cathode. Such devices required a threewire supply circuit,and in some cases are subject to arcing between the anodes.

In accordance with my invention I have provided gaseous dischargedevices, which operate with a long positive column discharge,- andhaving electrodes at opposite ends which function reversibly as cathodeand anode will respect to one another.

In thermionic gaseous devices having an elonated envelope in. which thedistance between the electrode is long relative to the distance of theelectrodes from the walls, the walls of the envelope appear to have agrid-like effect in resisting the starting of a discharge. Apparentlythe walls become negatively charged will not start through the gasbetween the electrodes until enough positive ions have been formed by ahigh voltage impulse to discharge the nega-' tive charge on the walls. Ihave discovered that in such an elongated envelope under suitableconditions successive electric discharges can be operated in oppositedirections without requiring the continuous operation of a-high voltageionizing means -oran operating voltage which is appreciably higher thana continuous or direct current discharge would require in an envelope ofthe same size and shape.

Apparently under suitable conditions of gas pressure and the geometricalrelation of the electrodes to one another and to the envelope, the' timerequired for a complete diffusion and discharge of the positive ions isgreater than the time d ring which, in an alternating current cycle, theimpressed voltage is too low to support a discharge.

My invention will be pointed out with greater particularity in theappended claims and will be more fully understood by reference to theac- 'companying drawing as explained by the following description.

In the drawing Fig. 1 is a perspective view of a and a discharge"gaseous glow lamp embodying my invention, part of the envelope beingremoved; Fig. 2 is a. longi-- tudinal section of an electrode andadjacent parts; and Fig. 3 is a diagram of anelectrical circuit suitablefor operating my improved lamp.

Referring to Fig. 1, the lamp illustrated comprises an elongated tubularenvelope 1, vconstituted of glass, quartz, or other suitable transparentmaterial, and having at opposite ends reentrant stems 2, 3, throughwhich pass respectively current conductors 4, 5 and 6, 7.

Upon these respective pairs of conductors are mounted the electrodes 8,9 each of which function alternately as cathode and anode. The structureof these electrodes is shown in detail in Fig. 2. As these electrodesoperate each alternately as anode and cathode they may be similar oridentical in structure. The electrodes illustrated comprise a'hollowbody or cylinder 10, which is heated by radiation or conduction or bothfrom a heater 11 which is located within the cylinder 10, the electriccircuit being constituted by the conductor 5 connected to one of theterminals of the heater 11, the cylinder 10, which is welded orotherwise joined to the oppo- 30 site terminal of the heater, and theconductor 5, to which the cylinder 10 is in turn joined. The cylinder 10which may consist of a foundation metal such as nickel, iron orplatinum, is coated with thermionically active material, such as analkaline earth oxide. For example, it may be coated with a layer ofbarium carbonate preferably admixed with a cellulose compound binder,the carbonate later being decomposed by heating the foundation metal toa temperature of about 1300 C. in a maintained vacuum. The heater 11consists of a suitable refractory metal .such as tungsten or molybdenum.Surrounding the cylinder 10 is a shield 12, which preferably isconnected to the conductor 5, and serves both to conserve the heatrequired for maintaining the cathode-at an operating temperature and toreduce deposition of evaporated cathode material on the wall of theenvelope.

Thermionic electrodes, such as herein described, having a broad emittingsurface are superior to ordinary filamentary cathodes for gaseous glowdevices and will be briefly referred to as broad cathodes. The surfacearea and electron emissivity of such a broad thermionic cathode shouldbe chosen to give a total electron emission which is capable ofsupporting the luminous discharge without causing thefall of potentialat the cathode to rise above the value at which the electricdisintegration becomes ap- 'ducing gas or vapor,'such illustrativeexample, a

- lower voltage.

preciable. If the high then the effect of positive ion bombardment onthe cathode is negligible and the lamps have a long life.

After the electrodes have been formed and degassed and the vitreousenvelope has been baked and evacuated of gas, a luminosity-proasneon,helium or mercury vapor is admitted. For example, neon at a pressure ofabout 1.5 to 3 millimeters of mercury may be employed.

As shown in Fig. 3, the terminals of the electrodes 8, 9 may beconnected to an auto-transformer 14 which is connected to a supplycircuit 15. The wiresi, 5 and 6, '1 are connected respectively by theconductors 16, 1'7 and 18, 19 to the sections 20 and 21 of thetransformer secondary for the supply'of electrode heating current. Inorder to start the lamp into operation a high potential impulse isimpressed upon it by any suitable means examples of which are wellknown.

For illustrative purposes, a starting device has been shown comprising amercury switch 22 which is connected to an intermediate point of thetransformer 14 through a resistance 23 and an end terminal by theconductor 24 in circuit with a magnet 25. When the supply circuit 15 isenergized the magnet 25 lifts its. armature 26, thereby interrupting theflow of current in'the switch circuit and impressing the resulting highvoltage impulse on the lamp terminals. These terminals when up totemperature are emitting electrons and ready to start into operation athermionic discharge when the high voltage discharge is impressed uponthem.-

'A discharge, when once started, will continue to operate at ordinarylighting circuit voltage, that is, the voltage of to 220 volts. As anlamp having a tubular envelope about 40 inches long (about one meter)and 1 inches (about 4 c. m.) in diameter provided with broad thermionicelectrodesat opposite ends, and containing neon. gas at a pressure oftwo millimeters of mercury may be operated steadily to produce aluminous discharge with alternating, sixty "cycle current of about oneampere and an impressed voltage of about 220 volts. A shorter lamp canbe operated with a Such a discharge willhave an over-all luminousefficiency of about 10 lumens per watt. A preponderate proportion of thevoltage consumed in such a lamp is consumed in the gaseous discharge andonly a small proportion at the electrodes.

electron emission is sufficiently cooperating electrodes, eachcomprising sealed envelope containing a What I claim as new and desireto secure by Letters Patent of the United States is:

1. An alternating current arc lamp comprising a sealed envelope, aluminosity-producing gas therein, and cooperating electrodes spacedapart a distance which is long relative to their size and comprisinghollow metal bodies, electric resistance heaters within said hollowbodies, leadingconductcrs therefor sealed into said envelope, and amaterial coating said hollow bodies having a higher electron emissivitythan said bodies, each of said hollow metal bodies having a surface areasuch that the anode drop in said lamp is substantially zero.

2. An alternating current positivecolumn arc lamp comprising anelongated tubular sealed envelope, a luminosity producing g'as therein,and cooperating electrodes located at opposite ends of said envelope andserving alternately as anode and cathode, a coating of ,material of highelectron emissivity on each of said electrodes, each of said electrodeshaving ,a surface area such thatthe anode drop in said lamp issubstantially zero.

3. An alternating current positive column are lamp comprising anelongated tubular sealed entherein, and a metallic body, a coating ofhigh electron emissivity on said body and a tubular metallic;shieldextending about said body and connected thereto, located atopposite ends of said envelope and serving alternately as anode andcathode, each of said electrodes having a surface of such area that theanode drop in said lamp is substantially zero.

4. An alternating current lamp comprising. a sealed envelope containinga luminosity-producing gas, cooperating electrodes therein which servealternately as anode and cathode, each of said electrodes having asurface of high electron emissivity, and means to heat each of saidelectrodes, the surface area af eacli of said electrodes being such thatthe anode drop in said lamp is substantially zero.

5. An alternating current iamp comprising a luminosity-producing gas andcooperating thermionic electronemitting electrodes which servealternately as anode and cathode, the surface area of each of saidelectrodes being such that the anode drop in said lamp is substantiallyzero.

velope, a luminosity producing gas CLIFTON G. FOUND

